Homebrew PCBs

Does anyone have any experience applying, exposing,
developing, etc. with Seno 1000 photoresist? This
is a positive-acting, dyed, aqueous developed and
stripped liquid photoresist. The only place that I've
found that sells it is Mega Electronics in the UK.

I'm interested in this because I have easy access to high
resolution laser photoplots and want to use photoresist
for board-making instead of toner transfer.

----- Original Message ----- 

From: "gregben" <gregben@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Thursday, June 24, 2004 7:41 AM
Subject: [Homebrew_PCBs] Seno 1000 liquid photoresist


> Does anyone have any experience applying, exposing,
> developing, etc. with Seno 1000 photoresist? This
> is a positive-acting, dyed, aqueous developed and
> stripped liquid photoresist. The only place that I've
> found that sells it is Mega Electronics in the UK.
>
> I'm interested in this because I have easy access to high
> resolution laser photoplots and want to use photoresist
> for board-making instead of toner transfer.

I've tried it. It works OK but I found it difficult to get an even film of
resist. It's probably OK with a bit of practise. I normally use the
pre-coated material.

Leon
--
Leon Heller, G1HSM
http://www.geocities.com/leon_heller

> The only place that I've found that sells it is Mega Electronics in
the UK.

Mega Electronics has a distributor in the US:
Vital Presentation Concepts, Inc.
www.vpcinc.com
info@...
1-800-648-2320

I just emailed them to find out if they have the Sena photoresist and
price.

Looks like they have a variety of prototype and short run PCB production
equipment and supplies.

If I get a positive response from them, I'll add a link in the links
section of the Homebrew_PCBs group web page.

Cheers,
- Jan

--- In Homebrew_PCBs@yahoogroups.com, "gregben" <gregben@y...> wrote:
> Does anyone have any experience applying, exposing,
> developing, etc. with Seno 1000 photoresist? This
> is a positive-acting, dyed, aqueous developed and
> stripped liquid photoresist. The only place that I've
> found that sells it is Mega Electronics in the UK.
> 
> I'm interested in this because I have easy access to high
> resolution laser photoplots and want to use photoresist
> for board-making instead of toner transfer.

My question is what are the things one looks for in a photo resist ?

dyed ?
positive ?
cost ? availability ?

What is available in the States at a reasonable cost ? and is that 
better then buying pre-coated boards ?

Dave

There was a gentleman on here that offered me coated boards last 
year, but never offered prices.

I am still mechanically etching, but after seeing that T-Tech go on E-
bay for $$$$ I may sell mine and buy Ballendos unit.

Dave

I use negative "dry-film" resist. I got about 20meters off a old 
roll from a local PCB shop. New film only sold in pair of rolls 
152.4 meter length 305mm width, price $AU600.

Application is tricky without the help from some basic tools. No 
need to buy a hot roll laminator. I got two rubber ink rollers 
from a old printing machine. I built a mounted frame so they roll 
against each other. I manually feed the PCB through the rollers 
while the film wraps around the top half of a roller, hanging 
down on the outside. Both the film and PCB go through the 
rollers. While laminating, warm water is slowly poured at the 
interface between the film and PCB as its feed through. This 
gives a lamination that is free from trapped air bubbles, dusk 
particles and wrinkles.
The PCB is then heated in drying oven at 90\ufffdC for 5 minutes and 
the film 'bakes' on. Its impossible to peel away the film after 
that. Developing and stripping are processed as normal.

The difficult part is finding a cheap printing press rubber 
roller. One of the rollers can be hard, like that from a old dot 
matrix, inkjet or laser printer.



gregben wrote:

> Does anyone have any experience applying, exposing,
> developing, etc. with Seno 1000 photoresist? This
> is a positive-acting, dyed, aqueous developed and
> stripped liquid photoresist. The only place that I've
> found that sells it is Mega Electronics in the UK.
> 
> I'm interested in this because I have easy access to high
> resolution laser photoplots and want to use photoresist
> for board-making instead of toner transfer.
>

> I got two rubber ink rollers from a old printing machine. I built a 
mounted frame so they roll against each other. 

Adam, do you have photos of the device you built? I'd love to 
see 'em. By "old printing machine," do you mean mean something from a 
printing shop printing press? What size are the rollers?

When you're laminating film to PCB, does not the film (cut larger 
than the plate?) adhere to the rollers?

Thanks much,

Brian Chapman
Cedar Rapids, Iowa


---

> The difficult part is finding a cheap printing press rubber 
> roller. One of the rollers can be hard, like that from a old dot 
> matrix, inkjet or laser printer.
> 
Possibility:  old washing machine wringer rollers (remember when?) 
or maybe industrial mop wringer rollers.  Just a thought.  

Wouldn't like to part with a little of that old film, would you?

Norm

nps0 wrote:

>  
> 
>>The difficult part is finding a cheap printing press rubber 
>>roller. One of the rollers can be hard, like that from a old dot 
>>matrix, inkjet or laser printer.
>>
> 
> Possibility:  old washing machine wringer rollers (remember when?) 
> or maybe industrial mop wringer rollers.  Just a thought.  

I haven't seen these rollers around. Ink rollers are precision 
molded and very smooth. Any lumps on the rollers will cause 
"dents" in the film. I got two secondhand rollers from a rubber 
roller manufacture. There are several manufactures around my city 
Melbourne, Australia. They all seem to make custom rollers, since 
each roller is different for each application so there is no such 
thing as an off the shelf rubber roller. I was lucky they had 
some old rollers laying around the factory floor. It turned out I 
only needed one rubber roller while the other could be any 
material/diameter, such as one scavenged from a desktop printer.

Another possibility is to get some rubber sheet feed that between 
  the film and a rollers. Then two hard rollers could be used. 
The idea would be to wet the film and rubber. Place film on 
rubber sheet so it adherers with water surface tension, i.e no 
wringles and completly conforms to surface of rubber sheet. Feed 
the rubber sheet with film into the rollers with the PCB and push 
it through. It would be much easier to have a handle on the shaft 
of one of the rollers so it can be wound by hand.
Hard rollers from printers have good precision and should work 
very well.


The film has clear protective layers on both sides. One 
protective side is made from mylar, and it is made very thin so 
photo mask can sits close as possible to its surface and avoid 
light undercut. The other side is polyethylene which is no 
different from cling food wrap. The protective polyethylene film 
is removed and it is this side of the resists which goes on the 
copper. The mylar film must remain on the other side of the 
resist since it must be present during UV exposure. Apparently 
atmospheric oxygen inhibits the photo polymerization of negative 
dry film resists.



> Wouldn't like to part with a little of that old film, would you?
I can give you a meter or so x 220 mm width, email me to discuss 
postage details. I haven't tried obtaining the data sheet. Its 
standard aqueous processable resist. Developed in 25 to 35\ufffdC 8 to 
10g/L Na2CO3 in tray with gentle wipe with paint brush. Stripped 
in room temp 20 to 80g/L NaOH, tray or immersion tank, soaked for 
2 to 10 minutes or until all resists lifts off copper, depending 
on temperature and period of time has been on board.